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The Purpose of a Titration

Every time a chemist needs to know exactly how acidic a sample of polluted water is, they rely on a highly precise technique called a titration. A titration is a quantitative method of volumetric analysis used to determine the concentration of an unknown solution. This is achieved by reacting it with a standard solution, which is a solution of accurately known concentration.

To perform a titration, a fixed volume of the unknown solution is measured into a conical flask using a pipette. The standard solution is added drop-by-drop from a burette. The reaction is complete at the end point, which is the precise moment the indicator permanently changes colour to signal neutralisation.

During this process, it is important to understand the components of the solutions involved:

Solute: The substance (usually a solid) that is dissolved.
Solvent: The liquid in which the solute dissolves.
Solution: The resulting mixture formed when the solute is dissolved in the solvent.

Practical Techniques and Indicators

Examiners expect you to know specific details about how a titration is set up to ensure high precision:

Burette precision: Readings must always be recorded to two decimal places, typically ending in $0.00$ or $0.05$ (e.g., ). You must read the volume at eye level from the bottom of the meniscus.

Titration	Rough	1	2	3
Final Reading ( $\text{cm}^3$ )	$24.50$	$23.90$	$23.30$	$23.40$
Initial Reading ( $\text{cm}^3$ )	$0.00$	$0.00$	$0.00$	$0.00$
Titre ( $\text{cm}^3$ )	$24.50$	$23.90$	$23.30$	$23.40$

Students frequently calculate the mean titre using the raw burette readings instead of the calculated titre volumes — always subtract the initial reading from the final reading first!

Examiners note that students often fail to spot the 1:2 molar ratio when sulfuric acid (H₂SO₄) is used in a neutralisation question, leading to a loss of marks.

In 4-6 mark titration calculations, examiners use "error carried forward" (ECF), meaning you should always clearly write down intermediate steps (like moles and ratios) to secure partial marks even if your final answer is wrong.

If a question asks why you only used specific runs to calculate your mean, the exact phrase required for the mark is "because they are concordant" or "because they are within 0.10 cm³ of each other."

A precise method of volumetric analysis used to calculate the unknown concentration of a solution by reacting it with a solution of known concentration.

A solution of accurately known concentration used in titrations.

The point in a titration where the indicator permanently changes colour, showing that neutralisation is complete.

The exact volume of liquid added from the burette to reach the end point in a titration.

Titre volumes that are within 0.10 cm³ of each other, demonstrating high precision.

The average volume calculated using only the concordant results from a titration experiment.

The ratio of the number of moles of each substance taking part in a reaction, as shown by the large numbers in the balanced chemical equation.

The number of moles of a dissolved solute per cubic decimetre (1 dm³) of solution.

The mass of a dissolved solute in grams per cubic decimetre (1 dm³) of solution.

The substance, often a solid, that is dissolved in a solvent to form a solution.

The liquid in which a solute dissolves to form a solution.

The mixture formed when a solute has dissolved in a solvent.

A trial titration performed quickly to find the approximate volume of titrant required to reach the end point.

A chemical indicator used in titrations that turns pink in alkaline solutions and colourless in acidic solutions.

A chemical indicator used in titrations that is yellow in alkaline solutions, red in acidic solutions, and orange at the end point.